CVE-2021-25395: Samsung Mobile Devices Race Condition Vulnerability

CVE-2021-25395 is a race condition vulnerability in the MFC charger driver on Samsung mobile devices. When radio privileges are already compromised, it can lead to a use-after-free condition that permits a write operation. This matters because mobile devices often hold sensitive corporate data, credentials, and access to enterprise resources; a successful exploit could expand an attacker's foothold from a limited radio-level compromise into further system control.

Defenders should treat this as a local privilege-related issue on affected Samsung hardware. Specifics such as exact device models or firmware builds must be confirmed against the vendor advisory, as public detail beyond the CISA summary is limited.

How it works

The underlying weakness is CWE-362, a concurrent execution using a shared resource with improper synchronization (race condition). In this case the race occurs inside the MFC charger driver. When an attacker who already holds radio privileges can win the race, the driver frees memory that is still referenced, creating a use-after-free. That dangling reference can then be abused to perform a write.

No public exploit mechanics, proof-of-concept code, or precise trigger sequences are provided in the available facts. Attackers would need prior radio-level access; the vulnerability itself does not grant that initial foothold. Treat any claims of remote unauthenticated exploitation as unverified until confirmed by the vendor advisory.

Am I affected? How to find it in your systems

The vulnerability affects Samsung mobile devices. These typically appear as employee-owned or company-issued smartphones and tablets running Samsung firmware, often managed through MDM or EMM platforms.

• Inventory all Samsung devices via MDM enrollment reports, asset databases, or network device discovery that captures manufacturer and model strings.
• Query device firmware or security-patch levels through the MDM console or by instructing users to check Settings > About phone > Software information. Compare the reported build against the fixed versions listed in Samsung’s security bulletin for CVE-2021-25395.
• Look for configurations that expose radio interfaces or allow untrusted apps elevated radio privileges; these increase the chance that the prerequisite compromise already exists.
• Telemetry signs of exploitation are not detailed in the facts. Monitor for unexpected kernel crashes, charger-driver related oops messages in logcat or kernel logs, or anomalous writes originating from radio-privileged processes. Correlate any such events with known indicators only after consulting the vendor advisory.

If your inventory process cannot determine the precise patch level, assume the device is potentially affected until proven otherwise.

How to remediate

The primary action is to apply the vendor-supplied updates. CISA directs organizations to “Apply updates per vendor instructions or discontinue use of the product if updates are unavailable.” Obtain the security patch that addresses CVE-2021-25395 from Samsung’s official channels and push it through your MDM or instruct users to install the OTA update promptly.

• Verify successful installation by re-checking the security-patch level on a sample of devices.
• After patching, re-baseline device configurations to ensure no residual elevated radio privileges remain unnecessarily granted.
• For devices that cannot receive the update (end-of-life models), follow the CISA guidance and plan to discontinue use or isolate them from sensitive networks.

Hardening steps appropriate to this class of race-condition / use-after-free issues include restricting apps that request radio-related permissions, enforcing least-privilege policies via MDM, and keeping the entire device software stack current so that subsequent driver fixes are also applied.

If you can't patch immediately

Until the vendor update can be deployed, reduce exposure with compensating controls:

• Segment affected Samsung devices onto restricted network segments that limit access to critical enterprise resources.
• Use MDM to disable or tightly control features that rely on the MFC charger driver or that grant radio privileges to third-party applications, if such options exist.
• Apply virtual patching or host-based controls where available (for example, SELinux policy refinements or kernel hardening modules that make use-after-free exploitation harder).
• Increase monitoring of radio-privileged processes and charger-driver related kernel events; alert on anomalies that could indicate an attempted race.
• If no update will ever be released for a given model, retire the device from corporate use as directed by CISA.

These measures lower risk but do not eliminate the underlying race condition; patching remains the definitive fix.

If your data may have been exposed

Actively exploited vulnerabilities on mobile devices can lead to data exposure or further lateral movement. Known ransomware use of this specific CVE is not documented. If you suspect compromise, preserve device logs, isolate the handset, and perform a forensic review. Separately, you can run a free exposure scan of your email addresses against known breach data sets to determine whether credentials or personal information have already appeared in public dumps.